The present invention relates to a new and improved apparatus for inflating an inflatable device such as a vehicle occupant restraint.
Known structures for inflating a vehicle occupant restraint are disclosed in U.S. Pat. Nos. 3,806,153, 3,868,124 and 3,895,821. In each of the structures disclosed in these patents, air, or other gas, and solid gas generating material are stored in a container. Upon the occurrence of a high rate of vehicle deceleration indicative of a collision, the gas in the container is released to inflate a vehicle occupant restraint which restrains a vehicle occupant during the collision. Also, upon the occurrence of a high rate of vehicle deceleration which is indicative of a vehicle collision, the gas generating material is ignited. As the gas generating material burns, it forms hot gases or vapors which heat and mix with the stored gas, and the heated mixture of gases flows into the occupant restraint.
The present invention provides a new and improved apparatus for inflating an inflatable device such as a vehicle occupant restraint. The apparatus includes a containing means for receiving gases to provide a combustible mixture of the gases. The apparatus also includes an igniter means for igniting the mixture of gases to warm and increase the pressure of gas in the containing means. The apparatus further includes a directing means which directs gas from the containing means to the inflatable device.
Preferably, the mixture of gases includes an inert gas, a flammable fuel gas and an oxidizer gas. The inert gas is preferably nitrogen or argon or a mixture of nitrogen and argon. The fuel gas is preferably hydrogen or methane or a mixture of hydrogen and methane but may be any other flammable gas. The oxidizer gas is preferably oxygen. Alternatively, the inert gas can be eliminated and a combustible gas mixture that is very fuel lean could be used. A small amount of an inert tracer gas such as helium may also be added to assist in leak checking the apparatus.
The containing means may take a variety of different forms. In one embodiment of the invention, the containing means is a single container for containing the inert gas, the fuel gas, and the oxidizer gas as a mixture of gases. Alternatively, the single container may contain the very fuel lean combustible gas mixture.
In another embodiment, a first container contains the fuel gas, a second container contains the oxidizer gas, and the containing means defines a combustion chamber which receives the fuel gas and oxidizer gas and in which the mixture of gases is ignited. In this embodiment the amount of oxidizer gas used is in excess of a stoichiometric amount to support combustion of the fuel gas.
In accordance with the present invention, the rate of inflation of the inflatable device can be controlled to provide a desired volume of the inflatable device at a given time after ignition of the fuel gas. The rate of inflation of and the pressure in the inflatable device can be controlled by selecting the amount of fuel gas and oxidizer gas to yield, a desired burning rate which in turn determines the predetermined volumetric rate of flow of warm gas into the inflatable device. Alternatively or additionally, the rate of inflation can be controlled by flow control orifices or the like through which the gas flows into the inflatable device. Another technique for controlling the time required for inflation is to change the number of locations in the containing means at which the fuel gas is ignited.
An improved igniter means is provided for igniting a mixture of gases. The igniter means is operable to transmit energy through an imperforate wall portion of the containing means. The energy transmitted through the imperforate wall portion of the containing means effects ignition of ignitable material in the containing means. Specifically, an ignitable charge located adjacent to an outer side of the imperforate wall portion of the containing means is ignitable to cause ignition of an ignitable charge which is disposed adjacent to an inner side of the imperforate wall portion of the containing means. In accordance with another feature of the igniter means, an elongated core in a frangible sheath is disposed in the containing means. The elongated core is ignited with a resulting shattering of the sheath and spewing of incandescent reaction products into the containing means.